Joint assembly

ABSTRACT

A joint assembly comprises an end portion of a first component that is accommodated within an end portion of a second component, with each respective first and second end portion having a corresponding first and second location feature, and an elongate resilient helical connection member. The second location feature comprises a proximal portion and a distal portion, with a clamping ring accommodated within the distal portion. When the joint is assembled, the first and second location features together define an annular cavity into which is accommodated the connection member to interlock the first and second components to one another. The clamping ring is adapted to exert a radially inwardly directed clamping force on the connection member.

This disclosure claims the benefit of UK Patent Application No.GB1417938.6, filed on 10 Oct. 2014, which is hereby incorporated hereinin its entirety.

FIELD OF THE INVENTION

The present invention relates to an improved joint assembly andparticularly, but not exclusively, to an improved joint assembly forlocking two components together, together with a method of using such ajoint assembly.

BACKGROUND TO THE INVENTION

It is known to use a wired joint to lock two cylindrical components toone another. Such an arrangement uses a wire having either a round(shown in FIG. 1) or square (shown in FIG. 2) cross section which isinserted into an annular cavity between the two components through aslot in the outer surface of the assembled components.

In order to ensure that the assembled components are held securelytogether, it is necessary for the wire to be a close fit in the annularcavity. The frictional forces resulting from this close fit makeinsertion, and particularly removal, of the wire difficult. This in turnrenders this joint arrangement impractical for applications, such as gasturbine engines, where a cylindrical joint needs to be made and brokenfor maintenance and repair without having to apply undue force.

Most gas turbine engines employ conventional nut and bolt configurationsto secure together the main structural engine components, such as fanand body casing parts. The temperature of gases passing through theengine can range between approximately 700° C. and approximately 2500°C. which can cause thermal cycling problems. As the engine temperaturevaries through such a temperature range, bolts tend to gall and seize.This can require the bolts to be drilled out during the disassembly ofthe engine, which is expensive and time-consuming. In addition, the useof nuts and bolts requires the use of corresponding flanges on the partsto be joined, which adds to weight and increases assembly time.Furthermore, in some arrangements, bolts heads are positioned in the gasflow path which may disrupt the aerodynamics of the engine and mayaccelerate the deterioration of the bolt.

The joint assembly of the present invention eliminates the requirementfor a nut and bolt configuration and so reduces weight, speeds assemblyand repair, minimises aerodynamic disruption in the flow path throughthe assembled components is simpler and less expensive than aconventional joint assembly, and reduces the high stress concentrationsand bending loads associated with a bolted flanged joint.

STATEMENTS OF INVENTION

According to a first aspect of the present invention there is provided ajoint assembly comprising an end portion of a first component,comprising a first location feature on an outermost surface thereof, anend portion of a second component, comprising a second location featureon an innermost surface thereof, the second location feature comprisinga proximal portion and a distal portion, an elongate, resilient, helicalconnection member, and a clamping ring, wherein the clamping ring isaccommodated within the distal portion of the second location feature,the end portion of the first component is accommodated within the endportion of the second component such that the first location feature andthe proximal portion of the second location feature are aligned to forman annular cavity, the connection member is receivable within theannular cavity to thereby interlock the first component and the secondcomponent to one another, and the clamping ring is adapted to exert aradially inwardly directed clamping force on the connection member.

The clamping ring exerts a radially inwardly directed force on theconnection member, which acts to press the connection member intocontact with a surface of the annular cavity, the surface being proximalto the end portion of the first component and distal to the end portionof the second component.

An advantage of the radially inwardly directed force exerted by theclamping ring is that it increases the stiffness of the joint assemblyby removing any clearance between the connection member and the annularcavity. This improves the structural efficiency of the joint assembly.

The use of a resilient, helical connection member will make the jointassembly easier to assemble and dismantle, since it's outer diameter canbe reduced on assembly and dismantling by stretching or twisting theconnection member along its length.

This makes the joint assembly of the present invention a viable optionfor use on a gas turbine and provides the associated benefits of abolt-less joint, a flush external joint surface, a lighter and cheaperassembled joint (particularly if the assembly costs are considered) andless distortion in the outer surface of the joined components.

By using a resilient, helical connection member instead of a solid wire,it is possible to reduce the access space required to assemble the jointdue to the flexible nature of the connection member. In addition, thereis no requirement to provide clearance for bolt withdrawal clearance orspanner movement.

In an alternative embodiment of the invention, the connection member maycomprise a plurality of spherical or cylindrical elements linkedtogether by a filament.

Optionally, the clamping ring is formed as a split ring and the secondcomponent further comprises a plurality of grub screws arranged radiallyaround and axially aligned with the distal portion of the secondlocation feature, and adapted to press against the clamping ring andthereby exert the radially inwardly directed clamping force on theconnection member.

The use of a plurality of grub screws arranged circumferentially aroundthe second component is a simple and cost-effective way to apply theradially inwardly directed clamping force on the connection member.

Optionally, the first component is a first revolute component and thesecond component is a second revolute component.

In one arrangement, the first and second components are cylindrical incross section. An advantage of such an arrangement is that the annularcavity can be arranged on the neutral axis of cylindrical componentwall. This minimises the bending loads on the joint which may resultfrom axial loading of the joint assembly.

In other arrangements, the first and second components may have completeor partial revolute cross-sections with an alternative geometry such as,for example, an ellipse.

In still further arrangements, the first and second components may havecorresponding multifaceted cross-sectional profiles. In sucharrangements, a plurality of connection members would be used with aseparate connection member for each facet. This arrangement could alsobe used to secure a bracket or mounting frame on to a casing or even anaxial split line in a casing where a complete circumferential interfacedoes not exist.

Optionally, the annular cavity has a rectilinear cross-sectionalprofile.

An annular cavity having a rectilinear cross-sectional profile providesa radially outermost surface against which the helical connection memberpresses in order to locate the first and second components together.

Optionally, the connection member is formed from a material having arectilinear cross-sectional profile.

By forming the connection member from a material with a rectilinearcross-sectional profile, the outer surface of the connection member hasa larger surface area. This means that any mechanical loads which aretransmitted through the joint are distributed over this larger surfacearea, thus reducing local surface stresses in the material within whichthe annular cavity is formed.

Optionally, the connection member is formed from a metallic material.

The joint of the present invention experiences lower peak stresses thanare present in a similarly sized bolted joint. Consequently, this jointarrangement is suited to manufacture from thin wall section metallicmaterials such as those used in gas turbine engines.

Optionally, the connection member is formed from a polymeric compositematerial.

As mentioned above, the lower peak stresses experienced by a jointassembly of the present invention make it well suited to joiningcomposite components.

Optionally, the connection member is formed from a material having agreater thermal coefficient of expansion than that of either of thefirst component or the second component.

By forming the connection member from a material having a greaterthermal coefficient of expansion than that of the components beingjoined, the joint is tightened when the components experience anincrease in temperature. In other words, as temperatures rise, forexample as a gas turbine engine reaches operating conditions, the jointbecomes more secure.

Conversely, as the joint assembly cools down, the joint clearancesincrease and the joint becomes easier to dismantle.

Optionally, the second component further comprises an insertion slot,the insertion slot being formed as an aperture tangentially aligned withthe second location feature.

The insertion slot provides access for a user to insert the connectionmember into the annular cavity once the first and second components havebeen assembled together.

In alternative embodiments of the invention, the insertion slot may bepositioned in the radially innermost surface of the first component. Inthis way, the insertion slot provides access for a user to insert theconnection member into the annular cavity from within the jointassembly. This may be more convenient in arrangements where the firstand second components are of significant diameter and access to theinterior of the joint assembly is more easily arranged than access tothe exterior of the joint assembly.

Optionally, the joint assembly further comprises a plurality ofelongate, resilient, helical connection members, each of the pluralityof connection members being receivable within the annular cavity tothereby interlock the first component and the second component to oneanother.

Depending on the length of the joint between the components, multipleconnection members could be used in order to reduce the frictional loadon each individual connection member during assembly. Each connectionmember would be provided with a discrete insertion slot.

In other arrangements of the joint assembly, additional grooves andsprings could be added. This would provide increased load carryingcapacity for the joint assembly.

Optionally, the joint assembly further comprises a closure member, theclosure member being accommodated within the insertion slot, with anoutermost surface of the closure member being contiguous with anoutermost surface of the second component.

The closure plate provides the outer surface of the assembled joint witha smooth surface. This may be advantageous if the surface is part of agas transfer path.

Optionally, the first component further comprises a third locationfeature at the first end portion thereof, and the second componentfurther comprises a fourth location feature at the first end portionthereof, wherein, when the first end portion of the first component isaccommodated within the first end portion of the second component suchthat the first location feature and the second location feature arealigned to form an annular cavity, the third location feature and thefourth location feature are interlocked with one another.

By providing the joint assembly with a separate spigot feature, it ispossible to increase the stiffness of the joint assembly and make thejoint more robust.

According to a second aspect of the present invention there is provideda method of joining two components using a joint assembly, the jointassembly comprising an end portion of a first component, comprising afirst location feature on an outermost surface thereof, an end portionof a second component, comprising a second location feature on aninnermost surface thereof, the second location feature comprising aproximal portion and distal portion, and an elongate, resilient, helicalconnection member, and a clamping ring,

-   -   the method comprising the steps of:        -   (a) inserting a clamping ring into the distal portion of the            second location feature;        -   (b) inserting the first end portion of the first component            into the first end portion of the second component such that            the first location feature and the second location feature            are aligned; and        -   (c) inserting an elongate, resilient, helical connection            member into an annular cavity formed by the alignment of the            first location feature and the proximal portion of the            second location feature such that the clamping ring exerts a            radially inwardly directed clamping force on the connection            member.

Optionally, the second component further comprising a plurality of grubscrews arranged radially around and axially aligned with the distalportion of the second location feature, and wherein step (c) comprisesthe steps of:

-   -   (c1) inserting the first end portion of the first component into        the first end portion of the second component such that the        first location feature and the second location feature are        aligned; and    -   (c2) tightening each of the grub screws to press against the        clamping ring and thereby exert a radially inwardly directed        clamping force on the connection member.

Optionally, step (b) further comprises twisting the connection memberalong its length while inserting the connection member into the annularcavity.

Optionally, step (b) further comprises extending the connection memberalong its length while inserting the connection member into the annularcavity.

An advantage of the invention is the ability to reduce the diameter ofthe connection member by either stretching or twisting the connectionmember axially to ease the insertion of the connection member into theannular cavity. The connection member can then be returned to itsoriginal diameter by reversing this motion to create a close or ‘snug’fit between the connection member and the annular cavity.

In addition, the connection member has a degree of lateral compliancewhich enables its insertion into the annular cavity to be largelyunaffected by the presence of minor machining mismatches between thefirst and second location features which together define the annularcavity.

Other aspects of the invention provide devices, methods and systemswhich include and/or implement some or all of the actions describedherein. The illustrative aspects of the invention are designed to solveone or more of the problems herein described and/or one or more otherproblems not discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

There now follows a description of an embodiment of the invention, byway of non-limiting example, with reference being made to theaccompanying drawings in which:

FIG. 1 shows a schematic sectional view of a wired cylinder jointaccording to the prior art and having a wire with a round crosssectional profile;

FIG. 2 shows a variant of the wired cylinder joint of FIG. 1 but havinga wire with a rectangular cross sectional profile;

FIG. 3 shows a perspective, part-sectional view of a joint assemblyaccording to a first embodiment of the invention;

FIG. 4 shows schematic perspective and sectional views of a connectionmember from the joint assembly of FIG. 3;

FIG. 5 shows a schematic sectional view of the joint assembly of FIG. 3including a spigot arrangement; and

FIG. 6 shows a schematic sectional view of a joint assembly according toa second embodiment of the invention.

It is noted that the drawings may not be to scale. The drawings areintended to depict only typical aspects of the invention, and thereforeshould not be considered as limiting the scope of the invention. In thedrawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

Referring to FIGS. 3 to 5, a joint assembly according to a firstembodiment of the invention is designated generally by the referencenumeral 100.

The joint assembly 100 comprises a first component 110, a secondcomponent 120, a connection member 140, and a clamping ring 144. Thefirst component 110 has a first end portion 112 with a first locationfeature 114 positioned on an outermost surface 113 thereof. The secondcomponent 120 has a first end portion 122 with a second location feature124 positioned on an innermost surface 123 thereof. The second locationfeature 124 comprises a proximal portion 127 and distal portion 128.

The end portion 112 of the first component 110 fits into, and isaccommodated within, the end portion 122 of the second component 120.

The clamping ring 144 fits into and is accommodated within the distalportion 128 of the second location feature 124 of the second component120. In the present embodiment, the clamping ring 144 is formed as asplit ring having a circular cross-sectional profile and made from ahigh strength alloy steel.

In other arrangements the clamping ring 144 may be formed with analternative cross-sectional profile, for example a polygonalcross-sectional profile.

The second component 120 further comprises a plurality of grub screws146 arranged radially around and axially aligned with the distal portionof the second location feature 124. The grub screws 146 have aconventional threaded form.

In other arrangements the clamping ring 144 may take the form of acircumferentially contractable band which may be tightened to bearagainst and exert a radially inwardly directed clamping force on theconnection member 140.

In an alternative arrangement (shown in FIG. 5), a spigot 180 may beincluded at the joint between the first component 110 and secondcomponent 120 to thereby improve the stiffness of the joint assembly.

In this embodiment, the spigot 180 comprises an interlocking arrangementof a third location feature 116 and a fourth location feature 126 (seeFIG. 4). The third location feature 116 is positioned at the end portion112 of the first component 110 while the fourth location feature 126 ispositioned at the end portion 122 of the second component 120.

In other embodiments of the invention, the spigot 180 may have adifferent number of location features.

When the end portion 112 of the first component 110 is located withinthe end portion 122 of the second component 120, the first locationfeature 114 and the second location feature 124 are aligned with oneanother to form an annular cavity 130.

The connection member 140 takes the form of an elongate, helical springwhich in turn is formed from flexible stainless steel wire with a squarecross-sectional profile (see FIG. 4). In other embodiments of theinvention, the connection member 140 may be formed from alternativematerials such as, for example, steel or other metallic materials, orpolymeric composite materials.

In case of breakage of the spring forming the connection member 140whilst in the joint assembly 100, the helical geometry of the connectionmember 140 would lend itself to having a screw threaded implementinserted and attached to the remaining part of the connection member 140by screwing into the remaining part of the connection member 140. Thiswould enable the extraction of the connection member 140 from theannular cavity 130.

The annular cavity 130 has a substantially toroidal shape at theinterface between the first location feature 114 and the proximalportion 127 of the second location, into which the connection member 140is received such that the first component 110 and second component 120are interlocked with one another.

When the connection member 140 is located within the annular cavity 130,the clamping ring 144 abuts against the connection member 140.

With the end portion 112 of the first component 110 located within theend portion 122 of the second component 120 and the connection member140 inserted into the annular cavity 130, each of the grub screws 146are tightened to thereby bear down on the clamping ring 144. This inturn results in the clamping ring 144 exerting a radially inwardlydirected clamping force on the connection member 140.

The end portion 112 of the first component 110 further comprises aninsertion slot 150. The insertion slot 150 is oriented substantiallytangentially to the first location feature 114 so as to provide anaperture extending through the thickness of the end portion 112 of thefirst component 110.

In the present embodiment, the insertion slot 150 is a linear apertureextending through the end portion 112 of the first component 110.

In other embodiments of the invention, the insertion slot 150 may beformed as a curved aperture, extending in the plane of the firstlocation feature 114, and having a concave portion facing outwardly fromthe outermost surface 113 of the first component 110. The curvedinsertion slot requires less circumferential distance than a linearaperture and still allows for the insertion of the connection member 140due to the inherent flexibility of the connection member 140.

A closure member 160 is provided to close off the insertion slot 150.The closure member 160 serves to infill the insertion slot 150 to thusprovide a smooth outermost surface 113 to the first component 110.

The closure member 160 comprises an anti-rotation element 162 whichserves to prevent rotation of the connection member 140 within theannular cavity 130. By preventing rotation of the connection member 140,it is possible to prevent fretting of the connection member 140 withinthe annular cavity 130.

The anti-rotation element 162 further serves to circumferentially locatethe first component 110 and the second component 120 relative to oneanother.

The connection member 140 is sized such that its outer diameter isslightly greater than the corresponding diameter of the annular cavity130.

In use, one end of the connection member 140 is rotated along its axialdirection relative to the opposite end. The direction of rotation isopposite in sense to the direction of the helix forming the connectionmember 140. This rotation causes the outer diameter of the connectionmember 140 to reduce. The connection member 140 may then be insertedinto the annular cavity 130. Once positioned within the annular cavity130 the connection member 140 may be allowed to rotate back to itsoriginal orientation.

In this way when the connection member 140 is positioned within theannular cavity 130, it is tensioned so as to provide a force directedsubstantially normal to the plane intersecting the first locationfeature 114 and the second location feature 124. This force maintainsthe connection member 140 in place within the annular cavity 130. Theforce also maintains the alignment of the first component 110 and thesecond component 120.

Referring to FIG. 6, a joint assembly according to a second embodimentof the invention is designated generally by the reference numeral 200.Features of the apparatus 200 which correspond to those of apparatusjoint assembly 100 have been given corresponding reference numerals forease of reference.

In this second embodiment (see FIG. 6), the joint assembly 200 comprisesa first component 110, a second component 120 and a plurality ofconnection members 240.

As described above, the first component 110 and second component 120interconnect with respective first and second location features 114,124thereby defining an annular cavity 130.

In this embodiment, the outermost surface 113 of the first component 110is provided with a plurality of insertion slots 250; each of theplurality of insertion slots 250 corresponding to a respective one ofthe connection members 240.

Each of the insertion slots 250 is provided with a respective closuremember 260. The closure members 260 function as the closure member 160described above.

Any of the embodiments described above may be provided with anelastomeric or metallic seal at the joint line between the first andsecond components to improve the seal and add a degree of axialcompression to ensure the joint is axially preloaded to restrict axialmovement.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to aperson of skill in the art are included within the scope of theinvention as defined by the accompanying claims.

What is claimed is:
 1. A joint assembly comprising: an end portion of afirst component, comprising a first location feature on an outermostsurface thereof; an end portion of a second component, comprising asecond location feature on an innermost surface thereof, the secondlocation feature comprising a proximal portion and a distal portion; anelongate, resilient, helical connection member; and a clamping ring,wherein the clamping ring is accommodated on an inner side of the distalportion of the second location feature, the end portion of the firstcomponent is accommodated on an inner side of the end portion of thesecond component such that the first location feature and the proximalportion of the second location feature are aligned to form an annularcavity, the connection member is receivable within the annular cavity tothereby interlock the first component and the second component to oneanother, and the clamping ring is adapted to exert a radially inwardlydirected clamping force on the connection member.
 2. The joint assemblyas claimed in claim 1, wherein the clamping ring is formed as a splitring and the second component further comprises a plurality of grubscrews arranged radially around and axially aligned with the distalportion of the second location feature, and adapted to press against theclamping ring and thereby exert the radially inwardly directed clampingforce on the connection member.
 3. The joint assembly as claimed inclaim 1, wherein the first component is a first revolute component andthe second component is a second revolute component.
 4. The jointassembly as claimed in claim 1, wherein the annular cavity has arectilinear cross-sectional profile.
 5. The joint assembly as claimed inclaim 1, wherein the connection member is formed from a material havinga rectilinear cross-sectional profile.
 6. The joint assembly as claimedin claim 1, wherein the connection member is formed from a metallicmaterial.
 7. The joint assembly as claimed in claim 1, wherein theconnection member is formed from a polymeric composite material.
 8. Thejoint assembly as claimed in claim 1, wherein the connection member isformed from a material having a greater thermal coefficient of expansionthan that of either of the first component or the second component. 9.The joint assembly as claimed in claim 1, wherein the second componentfurther comprises an insertion slot, the insertion slot being formed asan aperture tangentially aligned with the second location feature. 10.The joint assembly as claimed in claim 9, further comprising a closuremember, the closure member being accommodated within the insertion slot,with an outermost surface of the closure member being contiguous with anoutermost surface of the second component.
 11. The joint assembly asclaimed in claim 1, further comprising a plurality of elongate,resilient, helical connection members, each of the plurality ofconnection members being receivable within the annular cavity to therebyinterlock the first component and the second component to one another.12. The joint assembly as claimed in claim 1, the first componentfurther comprising a third location feature at the first end portionthereof, and the second component further comprising a fourth locationfeature at the first end portion thereof, wherein, when the first endportion of the first component is accommodated on an inner side of thefirst end portion of the second component such that the first locationfeature and the second location feature are aligned to form an annularcavity, the third location feature and the fourth location feature areinterlocked with one another.
 13. A method of joining two componentsusing a joint assembly, the joint assembly comprising an end portion ofa first component, comprising a first location feature on an outermostsurface thereof, an end portion of a second component, comprising asecond location feature on an innermost surface thereof, the secondlocation feature comprising a proximal portion and a distal portion, anelongate, resilient, helical connection member, and a clamping ring, themethod comprising: (a) inserting a clamping ring into the distal portionof the second location feature; (b) inserting the first end portion ofthe first component into the first end portion of the second componentsuch that the first location feature and the second location feature arealigned; and (c) inserting an elongate, resilient, helical connectionmember into an annular cavity formed by the alignment of the firstlocation feature and the proximal portion of the second location featuresuch that the clamping ring exerts a radially inwardly directed clampingforce on the connection member.
 14. A gas turbine engine comprising ajoint assembly as claimed in claim
 1. 15. The joint assembly as claimedin claim 1, wherein the clamping ring abuts the connection member. 16.The method as claimed in claim 13, wherein the second component furthercomprises a plurality of grub screws arranged radially around andaxially aligned with the distal portion of the second location feature,and wherein step (c) comprises: (c1) inserting the first end portion ofthe first component into the first end portion of the second componentsuch that the first location feature and the second location feature arealigned; and (c2) tightening each of the grub screws to press againstthe clamping ring and thereby exert a radially inwardly directedclamping force on the connection member.
 17. The method as claimed inclaim 13, wherein step (b) further comprises twisting the connectionmember along its length while inserting the connection member into theannular cavity.
 18. The method as claimed in claim 13, wherein step (b)further comprises extending the connection member along its length whileinserting the connection member into the annular cavity.